This invention relates to polyamines which contain urethane and/or urea groups and/or biuret groups and a process for the production of such polyamines.
It is known that aromatic isocyanates may be converted into primary amines by acid hydrolysis. However, this conversion reaction takes place only to a limited extent, because the amine formed during hydrolysis reacts with the unreacted isocyanate to form the corresponding urea. This secondary reaction cannot be suppressed even when excess strong mineral acid is used. (See e.g., Japanese Pat. No. 55007-827).
German Offenlegungsschrift No. 1,270,046 describes a process for the production of certain primary aromatic amines containing polyalkylene glycol ether segments. In this disclosed process, the reaction products of aromatic di- or tri-isocyanates with polyalkylene glycol ethers and/or polyalkylene glycol thioethers, (preferably those having molecular weights of from 400 to 4000,) are reacted with secondary or tertiary carbinols. The resultant mixture is then subjected to thermal dissociation in an inert solvent (optionally in the presence of acid catalysts). One disadvantage of this process is that, during the course of the thermal dissociation of the urethanes, combustible, volatile alkenes are produced. These alkenes are explosive when mixed with air, so suitable precautionary measures must be taken.
German Auslegeschrift No. 1,694,152 discloses production of prepolymers having at least two terminal amino groups by reacting hydrazine, aminophenylethylamine or other diamines with an NCO-prepolymer. Suitable NCO-prepolymers are made from a polyether polyol and a polyisocyanate (NCO: NH ratio=from 1:1.5 to 1:5). Unreacted amine must be carefully removed in the described process because the amine catalyzes the reaction with polyisocyanate (thereby causing short processing times) and also serves as a reactant.
French Patent No. 1,415,317 describes another possible synthesis for polyamines having urethane groups. In this process, NCO-prepolymers containing urethane groups are converted into the N-formyl derivatives by formic acid, and are subsequently saponified to give terminal aromatic amines. The reaction of NCO-prepolymers with sulphamic acid according to German Auslegeschrift No. 1,155,907 also yields compounds having terminal amino groups. Relatively high molecular weight compounds having aliphatic, secondary and primary amino groups may be obtained according to German Auslegeschrift No. 1,215,373 by reacting relatively high molecular weight hydroxyl compounds with ammonia in the presence of catalysts under pressure at elevated temperatures. U.S. Pat. No. 3,044,989 also discloses a method for making polyamines in which relatively high molecular weight polyhydroxyl compounds are reacted with acrylonitrile and subsequently subjected to catalytic hydration. According to German Offenlegungsschrift No. 2,546,536 or U.S. Pat. No. 3,865,791, relatively high molecular weight compounds having terminal amino groups and urethane groups may be obtained by first reacting NCO-prepolymers with enamines, aldimines or ketimines having hydroxyl groups and then hydrolyzing the reaction product.